Prior art of possible relevance includes the following U.S. Pat. Nos.: 3,596,740 issued Aug. 3, 1971 to Nau; 3,835,967 issued Sept. 17, 1974 to Kerr; 4,030,578 issued June 21, 1977 to Cacciola et al; 4,176,733 issued Dec. 4, 1979 to Twickler; and 4,318,304 issued March 9, 1982 to Lang. Of the foregoing, the above-identified Twickler patent is perhaps the most relevant.
In the operation of many types of apparatus wherein a power source drives a load, there arises the possibility that the load, due to various forces may have a tendency to drive the power source. There also arises the possibility that excessive force may be transmitted between components of the system.
One environment where either possibility can cause difficulties is in the movement of control surfaces, such as flaps, in aircraft. There are, of course others, such as winches or the like.
In any event, it is customary in many such environments to provide "no-back" means which prevent the load from driving or overrunning the power source. It is likewise common to provide means for limiting the amount of force that can be transmitted through a mechanism. It is further common to incorporate both a no-back feature and a torque limiting feature in a mechanism used to transmit power from a power source to a load. However, as can be seen from many of the above identified patents, it is customary, where both no-back and torque limiting features are employed, to effectively employ them in tandem, that is, as two separate mechanisms. The sole exception is that represented by the above-identified Twickler patent which provides a no-back feature and a torque limiting feature in a single package.
Twickler combines both a no-back feature and a torque limiting feature into one package and is a torque sensing and torque limiting device, while the invention disclosed herein is a force sensing, force limiting device that incorporates a no-back feature by the sensing of force and direction of rotation. The mechanism is intended to limit output of a device that is axially loaded whereby it provides a more direct and compact means of incorporating these features than pure rotary devices, such as Twickler.
Both compactness and simplicity are highly desirable when a mechanism having both no-back and force limiting features are utilized in aircraft since compactness will most frequently provide a weight saving and simplicity may provide improved reliability, both highly desirable in aircraft constructions.